1. Field of the Invention
The present invention relates to control technology for a network plug-and-play compliant network relay device.
2. Description of the Related Art
Plug-and-play is a well-known technology that enables peripheral devices to be connected to a computer or disconnected from a computer at arbitrary timing after computer startup. In recent years, extension of plug-and-play technology to networks has led the development of Universal Plug and Play (hereinafter UPnP; UPnP is a trademark of UPnP Implementers Corporation). The use of UPnP enables network devices to be connected to a network or disconnected from the network at arbitrary timing. Herein, the architecture for realizing such plug-and-play capability in a network shall be termed “network plug-and-play.”
UPnP compliant network devices are able to function as service devices of various kinds. Here, “service device” refers to a device for executing a particular service in response to an external request. Service devices can be realized as devices of various kinds (termed “device units”), such as a printer, scanner, fax, copier, memory device, camera, clock or the like. It is also possible for the functions of several service devices to be realized by a single device unit.
It would be desirable if, through the use of a UPNP protocol compliant network relay device, non-UPnP compliant device units could be utilized as UPnP protocol compliant devices as well. However, to date, there has not yet been conducted sufficient research to how such a relay device would be achieved. For example, there has yet to be devised satisfactory means for notifying other clients in the event that a service device is not operating normally. As a result, even when a service device is not operating normally, clients will continue to attempt to utilize the device, and this represents wasted communication which reduces the communication efficiency of the network as a whole.